Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 48, NWS Philadelphia/Mount Holly

July 3, 2021Bucks County, Lehigh County, Northampton County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood advisory at Jul 3, 2021, 6:39 PM EDT for Bucks County, Lehigh County, Northampton County, Pennsylvania. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Jul 3, 2021, 6:39 PM EDT (22:39 UTC)
Expired
Jul 3, 2021, 8:54 PM EDT
In force
2 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon

Counties Bucks County, PA, Lehigh County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 107 km from the middle of the area, began a volume at 22:40 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 10.7 hours before the alert went out and 217 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Brookhaven, NY at 12:00Z on 2021-07-03Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Brookhaven, NY at 12:00Z on 2021-07-03The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 98 square meters per square second.1939587897117136Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
3326 m above ground
0-6 km bulk shear
46 kt
0-1 km storm-relative helicity
98 m²/s²
0-3 km storm-relative helicity
112 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

025 
WGUS81 KPHI 032239
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
639 PM EDT Sat Jul 3 2021

PAC017-077-095-040145-
/O.NEW.KPHI.FA.Y.0048.210703T2239Z-210704T0145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Bucks PA-Lehigh PA-Northampton PA-
639 PM EDT Sat Jul 3 2021

The National Weather Service in Mount Holly has issued a

* Flood Advisory for...
  Southeastern Lehigh County in eastern Pennsylvania...
  South Central Northampton County in eastern Pennsylvania...
  Northwestern Bucks County in southeastern Pennsylvania...

* Until 945 PM EDT.

* At 639 PM EDT, Doppler radar indicated heavy rain. Minor flooding 
  is ongoing or expected to begin shortly in the advisory area.

* Some locations that will experience flooding include...
  Allentown, Bethlehem, Emmaus, Quakertown, Hellertown, Pleasant 
  Valley, Springtown, Lehigh University, Fountain Hill, Coopersburg, 
  Richlandtown, and Trumbauersville.

This includes the following highways...
	Interstate 78 in Pennsylvania between mile markers 58 and 67.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be aware of your surroundings and do not drive on flooded roads.

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 4059 7553 4063 7546 4066 7540 4044 7516
      4037 7533

$$

MPS
2 follow-up statements
273 
WGUS81 KPHI 040005
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
805 PM EDT Sat Jul 3 2021

PAC017-077-095-040145-
/O.CON.KPHI.FA.Y.0048.000000T0000Z-210704T0145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Bucks PA-Lehigh PA-Northampton PA-
805 PM EDT Sat Jul 3 2021

...FLOOD ADVISORY REMAINS IN EFFECT UNTIL 945 PM EDT THIS EVENING 
FOR SOUTHEASTERN LEHIGH, SOUTH CENTRAL NORTHAMPTON, AND NORTHWESTERN 
BUCKS COUNTIES...

At 805 PM EDT, Doppler radar indicated that the heaviest rain has 
ended and moved out of the advisory area. However, several bands of 
light to locally moderate rain will continue. Minor flooding is 
ongoing in the advisory area.

Some locations that will experience flooding include...
  Allentown, Bethlehem, Emmaus, Quakertown, Hellertown, Pleasant 
  Valley, Springtown, Lehigh University, Fountain Hill, Coopersburg, 
  Richlandtown, and Trumbauersville.

This includes the following highways...
	Interstate 78 in Pennsylvania between mile markers 58 and 67.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 4059 7553 4063 7546 4066 7540 4044 7516
      4037 7533

$$

MPS
665 
WGUS81 KPHI 040054
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
854 PM EDT Sat Jul 3 2021

PAC017-077-095-040104-
/O.CAN.KPHI.FA.Y.0048.000000T0000Z-210704T0145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Bucks PA-Lehigh PA-Northampton PA-
854 PM EDT Sat Jul 3 2021

...FLOOD ADVISORY IS CANCELLED FOR SOUTHEASTERN LEHIGH, SOUTH 
CENTRAL NORTHAMPTON, AND NORTHWESTERN BUCKS COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 4059 7553 4063 7546 4066 7540 4044 7516
      4037 7533

$$

MPS

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 3, 1:38 PM EDTSpecial Weather StatementPHIDelaware52 min
Jul 3, 2:03 PM EDTAreal Flood AdvisoryPHIDelaware2 hr

Nearby

Areal Flood Advisories in Pennsylvania, 2021Every areal flood advisory in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.